Method of recording a control program



Nov. 9', 1965 T. A. wl-:Tzl-:L ETAL 3,217,331

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METHOD OF RECORDING A CONTROL PROGRAM 8 Sheets-Sheet 6 Original Filed May 18, 1959 AAV@ Nov. 9, 1965 T. A. wr-:TzEL ETAL 3,217,331

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METHOD OF RECORDING A CONTROL PROGRAM 8 Sheets-Sheet 8 Original Filed May 18, 1959 y 1 -1- BY im j Mm www United States Patent O 3,217,331 METHOD OF RECORDING A CONTROL PROGRAM Theodore A. Wetzel and Thomas A. Stoner, Brookfield, Wis., assignors to Kearney & Trecker Corporation, West Allis, Wis., a corporation of Wisconsin Original application May 18, 1959, Ser. No. 813,958, now Patent No. 3,127,613, dated Mar. 31, 1964. Divided and this application July 9, 1963, Ser. No. 293,726 Claims. (Cl. 346-1) This patent application constitutes a division of our co-pending U.S. Patent application, Serial No. 813,958, now U.S. Patent 3,127,613, and relates generally to an improved method for recording a program of machine operations for the purpose of establishing a record which may be employed for controlling the machine to cause the latter to operate in accordance with the recorded information.

Many automated production facilities have been designed to be operated in response to recorded information. In such an arrangement the control data is recorded and the record is subsequently employed for controlling the operation of the facility. The particular recorded operation may then 'be repeated by repeatedly utilizing the information that has been stored on the record.

For example, data may be recorded on either magnetic or punched tape for controlling a specific machine tool operation. When it is desired to perform the recorded operation, the record is played back and the information obtained therefrom is employed for controlling the relative movement between a cutting tool and a workpiece to perform the required machining operation on the workpiece. The same machine loperation may be repeated by repeating the playback -of the record and utilizing the information stored thereon for controlling the operation of the machine to produce the desired relative movement between the cutting tool and the workpiece.

The preferred system for preparing the control record is to feed the information concerning the operation t-o be performed into a computer or similar equipment which records the data in a form that may be subsequently employed for controlling the operation of the machine. For example, the information on a drawing of a workpiece which is to be machined may be converted to locate various points of the workpiece in relation to the datum or zero point of X and Y coordinates. This data is then utilized in the computer for preparing the record. However, the method for recording such control data and for converting it into a form which may be employed for actuating the control circuit of the machine to regulate its operation in the required manner has been complex and relatively expensive.

It is therefore a general object of the present invention to provide an improved method for creating a record which may be subsequently employed for controlling the operation of a machine.

Another object of the present invention is to provide a relatively inexpensive and simple method for recording data which may be subsequently utilized, from the record, for controlling the operation of a machine.

Another object is to provide a method for creating a record which may be played back for controlling the operation of a machine.

According to this invention an improved method is provided for recording data to establish a record which may 4be subsequently played back to furnish control signals for regulating the Eoperation of a machine to cause it to perform the specified operation. The method comprises of resolving a single input of numerical data representative of a cutter path -of travel to obtain two sinecosine related variable components. The two compo- Vice nents are utilized to produce signals which are converted to pulses and recorded on a record, such as magnetic tape. The signals are related to a reference signal which is likewise recorded on the record. Each of the two components represents the movement of one of two machine tool slides that are represented as moving along the axes of X land Y coordinates since the path of travel of one of the slides is perpendicular to Ithe path of travel of the other. It is apparent that a combined movement of the two slides will produce a resultant movement in a direction that is displaced angularly from both of the X and Y axes.

Each of the two variable components are adapted to produce a series of pulses on an associated channel on the record with the pulse varying in frequency in accordance with the variation in the rate of rotation of the component. One of the two components is adapted to regulate the frequency of the pulses for the machine tool slide motion along the X axis and is therefore referred to as the X component with the pulses being recorded on the X channel of the record. The other component is adapted to regulate the frequency of the pulses for the machine tool slide motion along the Y axis and is therefore referred to as the Y component with the pulses being recorded on the Y channel of the record. In addition to the X and Y channels, the record is provided with a third channel, which is termed the reference channel for receiving reference pulses that are recorded at a constant predetermined frequency at the same time that the pulses are being recorded on the X and Y channels.

On playback, the frequency of the pulses on the X and Y channels is compared with the constant frequency of the reference channel and a deviation therefrom produces a signal that serves to regulate the machine tool slide motion. Thus, if the frequency on either the X or the Y channels corresponds to the frequency of the reference channel, the corresponding machine tool slide will remain at rest. A frequency on either the X or Y channels that is greater than the frequency on the reference channel calls for a slide motion in one direction while a frequency on the X or Y channels that is less than the reference frequency establishes a slide motion in the opposite direction. Furthermore, the rate of travel of the X and Y machine tool slides varies directly as the frequency of the X and Y channels respectively varies from the reference channel. Thus, a frequency on the X channel which is greater than the frequency of the reference channel indicates a movement of the X machine tool slide in one direction and the greater the requency on the X channel above the frequency of the reference channel, the faster the X slide will travel. On the other hand, a frequency on the X channel which is iess than the reference frequency indicates a movement of the X slide in the opposite direction at a rate of travel which increases as the frequency of the pulses on the X channel decreases below the reference frequency. By thus controlling the movement of the machine tool slides, the relative movement between a cutting tool and a workpiece can be established to complete the desired machining operations on the workpiece.

The foregoing and others objects of the invention, which will become more fully apparent from the following detailed specification, may be achieved by means of the exemplifying embodiments, depicted in and described in connection with the accompanying drawings, in which:

FIGURE 1 is a left, front perspective view of apparatus which may be utilized to practice the teachings of the present invention;

FIG. 2 is a right, rear perspective view of the apparatus shown in FIG. 1;

aaizss 1 FIG. 3 is a view in vertical section through the column of the apparatus taken in a plane through the center of the mechanical resolver to show the various transmission drives, the tape transport housing having been omitted for the purpose of clarity, the showing being made as it would appear from the right side of the apparatus;

FIG. 4 `is a view partly in horizontal section and partly in plan illustrating the sphere of the mechanical resolver with its cooperating power take-ofi wheels;

FIG. 5 is a View partly in vertical section and partly in plan taken through the apparatus to illustrate the steering transmission and the drive wheel transmission torque motors showing them operatively connected to their respective transmissions and to show a portion of the transmission for the sine-cosine mechanism;

FIG. 6 is a fragmentary view partly in vertical section and partly in elevation taken in a plane represented by the line 6 6 in FIG. 7 to illustrate the take-ofi drive from the sphere to the X mechanical pulser;

FIG. 7 is a fragmentary view mostly in right side elevation illustrating the mechanical pulsers for the X reference, and- Z axes with parts of the front wall of the differential support being broken away to show the internal gearing arrangement;

FIG. 8 is a schematic block diagrammatic representation of the basic components employed in the present invention operatively connected to record an X channel and the reference channel on magnetic tape;

FIG. 9 is an enlarged View partly in vertical section and partly in elevation taken along the plane represented by the line 9-9 in FIG. 10 to show the steering rate changer for establishing a radius;

FIG. l0 is a view partly in horizontal section and partly in plan taken along the plane represented by the line 10-10 in FIG. 2, depicting the speed changer and rate changer gear box to show the relationship and arrangement of the associatedl dial transmissions;

FIG. 11 is a schematic representation showing the relationship and arrangement of the various transmissions connected to drive the mechanical pulsers;

FIG. 12 is a View partly in elevation `and partly in section taken along the plane represented by the line 12--12 in FIG. 7 to illustrate the Z axis mechanism;

FIG. 13 is a plan view of a workpiece shown orientated in the positive quadrant as related to the X and Y axes of Cartesian coordinates and showing the points which are to be used to describe the figure numerically in relation to the X and Y coordinates;

FIG. 14 is a chart in which the X and Y coordinates of the various points of the workpiece configuration shown in FIG. 13 are given; and,

FIG. 15 is a fragmentary view in Vertical section taken along the plane represented by the line 15-15 in FIG. 13, showing the workpiece supported on a table of a machine tool, the showing being made for the purpose of illustrating the path of travel of the cutter when controlled from Z information.

Reference is now made more particularly to the drawings and specifically to FIGS. l, 2 and 3 which illustrate a recording apparatus which may be utilized to practice the teachings of the present invention. The exemplary embodiment includes an upstanding pedestal or column generally identified by the reference numeral and having a hollow base casting 21 which encloses an electric motor 22 as shown in FIG. 3. The hollow base casting 21 supports a built up transmission housing that comprises a lower casting 23 secured to the top surface of the base casting 21, and intermediate or main casting 24 having an axial bore 25 and mounted on the top surface of the lower casting 23, a lower transmission casting 26 supported on the top surface of the intermediate casting 24, an upper transmission casting 27 secured to the top surface of the casting 26, and a top casting 28 of generally rectangular configuration which is mounted upon the top surface of the upper transmission casting 27. The several 4 castings carried by the base casting 21 cooperate to form a unitary housing for enclosing a transmission mechanism.

The control information developed by the apparatus of the present invention is recorded on a magnetic tape 35 as it passes over a recording surface 46 of a recording head 44. The magnetic tape 35 is passed through the recording head 44 by a tape transport mechanism of conventional construction that is generally identified by the reference numeral 3f) and is carried by an upstanding hollow housing 31. The transport mechanism includes a tape supply reel 32 from which the tape is drawn for passage through the recording head and after passing through the recording head 44 the tape is wound into a tal e-up reel 71.

The operation of the apparatus requires that the tape 35 travel past the recording surface 46 at a rate that is maintained in an exact relation to the rate of operation of the transmission mechanism which regulates the recording of the information on the tape. In order to achieve this relationship, the power for moving the tape 35 past the recording surface 46 is derived from such transmission mechanism by means of a capstan drive 48.

The capstan drive 48 comprises a tubular spindle carrier 49, as shown in FIG. 3, in which antifriction bearings 51 and 52 are mounted within suitable recesses formed in either end thereof. The bearings 51 and 52 serve to rotatively support a capstan spindle 53, the inner end of which is provided with a worm gear 54 which is keyed to the capstan spindle 53 for rotation therewith. A snap ring 55 is fixed to the capstan spindle 53 adjacent to the bearing 52 for maintaining the assembly within the carrier 49. The assembled carrier is inserted within a horizontal bore 56 provided in the upper transmission casting 27. The other end of the tubular carrier 49 is provided with an annular flange 57 through which bolts extend into threaded engagement with suitable threaded openings in the casting 27 to secure the carrier 49 within the bore 56.

The outer extending portion 58 of the capstan spindle 53 extends outwardly of the carrier 49 and through the housing 31, as clearly shown in FIG. 2. The capstan spindle 53 is driven by the transmission mechanism through a power train to be subsequently described and its extending end 58 is adapted to be in frictional engagement with the tape 35 so that as the extending end 58 of the capstan spindle 53 is rotated, it operates to draw the tape 35 past the recording surface 46 while the recording head 44 is being actuated by the apparatus to record the control data on the tape 35.

The peripheral surface of the end 5S of the capstan spindle 53 is provided with a highly polished surface over which the magnetic tape is entrained. The tape 35 is maintained in firm engagement with the polished extending end 58 of the capstan spindle 53 by a loading roller 61 which is urged by a compression spring 65 toward the extending end 58 to maintain the magnetic tape 35 in firm frictional driving engagement with the extending end 58, the magnetic tape passing between the extending end 58 and the loading roller 61.

In operation, the spindle 53 is rotated in a clockwise direction, as viewed in FIG. 2, to move the magnetic tape 35 across the recording surface 46 of the recording head 44 at the desired rate. As the extending end 58 rotates with the spindle 53, it operates to draw the tape off of the supply reel 32 and against the torque of a motor (not shown) that is associated with the supply reel 32. From the capstan drive 48, the processed magnetic tape is directed to the take-up reel 71 which is urged in a rotary movement by a suitable motor (not shown) to wind the tape about the reel. Therefore, as the capstan drive 48 operates to move the magnetic tape over the recording surface 46 of the recording head 44 the processed tape is wound on the reel 71, with the torque that is applied to the reel 71 being only sufficient to maintain a very slight tension on the tape.

The recording head 44 is comprised of a plurality of sections with each section functioning to record information on a separate channel of the magnetic tape 35. A separate channel is recorded on the tape for each machine tool slide that is to be controlled in response .to the recorded information, and in addition, another channel serves to receive a reference signal with which the control signals on the tape for the machine tool slide are compared to determine the required slide motion. Other channels may likewise be provided for recording pertinent information. For the illustrated embodiment of the present invention it will be assumed that the recording and playback will be performed with the magnetic tape traveling through the recording head 44 at a rate of 1% per second, and a reference frequency of 60 cycles per second is recorded on the tape.

Reference is now made to FIG. 8 which presents a diagrammatic illustration of the basic components of the apparatus of the present invention connected to produce control data for regulating the motion of the machine tool slide along the X axis. All of the power for actuating the several components is derived from the constant speed motor 22. In the diagram of FIG. 8, the various components are represented diagrammatically and are interconnected by lines which indicate a driving connection between the components.

Thus, the motor 22 is connected to drive the capstan spindle 53 through a transmission 72 which operates to reduce the output of the motor 22 for rotating the capstan spindle 53 at the required rate to obtain the desired rate of travel of the magnetic tape 35 past the recording head 44.

As previously mentioned, the information which is recorded is produced by the operation of the mechanical resolver which is generally identified in FIG. 8 as well as in FIG. 3 by the reference numeral 144. The particular mechanical resolver illustrated in the drawings is the type known as a ball transmission which will be subsequently described in greater detail. Briefly stated, the ball transmission comprises a sphere mounted for rotation about an inlinite number of axes and from which originate the drives for producing the data that is to be recorded. An input to the resolver serves to rotate the sphere, which, in turn, resolves the input into two components in a sinecosine relationship, one component serving to actuate the mechanism for recording the X axis of motion while the other component actuates the mechanism for the Y axis of motion with only the drive for the X axis of motion being depicted in FIG. 8. The sphere is rotated by a drive wheel which is in rictional engagement with the sphere, the drive wheel being rotated about its own axis by the input to the resolver. In addition, the drive wheel may be steered to change the position of its axis and thereby change the position of the axis of rotation of the sphere to vary the distribution of the input between its two components with the distribution between the two components always remaining in a sine-cosine relationship.

It is therefore apparent that the resolver 144 requires two inputs, one of which functions to rotate the sphere and the other of which functions to change its axis of rotation. To this end, the motor 22 is connected to drive the reduction transmission R1 the output of which is connected to eiiect rotation of the sphere of the resolver 144 and Ithereby constitutes the input which is resolved by the resolver 144 into the two components that represent the motion along the X and Y axes. The output of the transmission is also connected to drive the steering reduction transmission Rs which, in turn, is connected to the resolver 144 to provide power steering of the drive wheel for varying the distribution of the input between its two components. Thus, the transmission R1 reduces the speed of the output of the motor 22 and this reduced output of the motor 22 constitutes the input which is divided into the two components by the resolver 144. In addition, the speed of the output of the transmission R1 is vfurther reduced by a transmission Rs and the output of the latter is employed for adjusting the resolver 144 6 to vary its distribution of the input amongst its two com-s ponents.

The reduction transmissions R1 and Rs are each actually comprised of three independent transmissions that function in conjunction with each other to achieve the desired results. Thus, the transmission R1 incorporates a change gear transmission generally identified by the reference numeral 73 and which comprises a plurality of gears adapted to be changed in well known manner to vary the gear ratio. The change gear transmission 73, in turn, is connected to drive an infinitely variable speed changer 118 which in the particular embodiment is adapted to either increase or decrease the output speed of the change gear transmission. The reduction transmission R1 also includes a iixed gear transmission 74 in which the transmission ratio is not adjustable.

In like manner, the steering transmission Rs comprises three independent transmissions for producing the desired speed ratios in the drive for adjusting the resolver 144. Thus, the output of the reduction transmission R1 is directed to a change gear transmission 75 which comprises a plurality of replaceable gears for varying the gear ratio. From the change gear transmission 75 the drive is directed to an iniinitely variable speed changer 242 which is similar in construction and operation to the speed changer 118 of the reduction transmission R1. From the speed changer 242 the drive continues to a fixed gear transmission 265 that connects it to the resolver 144 for adjusting the latter to vary the distribution of its input amongst its two components.

As previously mentioned, only the X drive is illustrated in FIG. 8 as emanating from the resolver 144 but it is to be understood that an identical drive train is actuated by the resolver 144 for the Y axis of motion as will be subsequently described. The X component of the resolver 144 is directed to a reduction transmission R0, and the line in FIG. 8 which represents the connection between the resolver 144 and the transmission Ro is identified by the letter X to indicate that it is the X component of the resolver. The transmission R0 comprises a change gear 356 and a iixed gear transmission 76 which connects with one side of a differential mechanism that is generally identied by the reference numeral 295. The input to the ditlerential mechanism 295 by the X component of the resolver 144 through the transmission Ro is compared with a reference input of a constant speed that is directed to the differential mechanism from the motor 22. In FIG. 8, the connection from the motor 22 to the differential mechanism 295 is represented by a line which is identitled by the reference numeral 77.

The dilierential mechanism 295 algebraically adds the reference input and the X component input and this algebraic sum constitutes the output of the differential mechanism 295 which is recorded in the form of pulses at a frequency which varies in accordance with the variation of .the output of the differential mechanism. In order to produce these pulses for recording on the -magnetic tape, the output of the differential mechanism 295 is connected to drive a mechanical pulsing mechanism which is generally identified by the reference numeral 430 and which is connected to actuate an electronic iiip-liop circuit 78 that produces the pulses which are recorded on the magnetic tape, these pulses appearing on the magnetic tape as changes in polarity or alternate north and south poles on the tape.

The actuation of the iiip-ilop circuit 78 is produced by a pair of normally closed switches 437 and 438 that are operated by a disc cam 435 as the latter is rotated by the output of the diiierential 295. Actuation of one of the switches causes the iiip-iiop circuit to produce a positive impulse for recording on the magnetic tape while actuation of the other switch produces a negative impulse. It is apparent, therefore, that the frequency of the pulses depends upon the rate of rotation of the disc cam 435. As the output of the differential mechanism 295 increases the rate of rotation of the disc cam 435, the frequency of the pulses increases accordingly, and as the output of the differential mechanism 295 decreases the rate of rotation of the disc cam 435, the frequency of the pulses recorded on the tape will likewise decrease.

At the same time that the X axis pulses are being recorded in response to the operation of the X mechanical pulser 430, a reference mechanical pulser generally identified by the reference numeral 460 is being operated at a constant rate by the mot-or 22. It will be noted in FIG. 8, that the reference mechanical pulser 469 is connected to be driven from the drive train that transmits the reference input to the differential mechanism 295. The drive is connected to rotate a disc cam 461 which operates to actuate two switches 463 and 464 for reversing the polarity produced by a ip-flop circuit 79 to which the switches 463 and 464 are connected. The reference mechanical pulser 460 is identical in construction and operation to the pulser 430 but instead of being operated at a variable rate as is the pulser 439, the reference pulser is operated at a constant rate by the constant speed motor 22. The flip-flop circuit 79 is connected to a separate section of the recording head 44 for the purpose of recording a reverse polarity each time one of the switches 463 and 464 is actuated in response to the operation of the disc cam 461. However, since the disc ca-m 461 is being rotated at a constant rate, the changes in polarity which constitute the pulses on the magnetic tape will be of a constant frequency in contrast to the variation in the frequency of the pulses produced by the X flip-dop circuit 78, the latter pulses being recorded on the channel while the pulses in response to the operation of the flip-flop circuit 79 are recorded on a second channel.

On playback, the frequency of the pulses recorded on the X channel of the magnetic tape by operation of the X pulsing mechanism 430 is compared with the constant frequency of the pulses recorded on the reference channel of the tape by the operation of the reference pulsing mechanism 460 and the difference between these two frequencies determines the motion of the machine tool slide along the X axis.

Thus, for the purpose of the present description it will be assumed that the reference pulser 460 is operated by the motor 22 at a rate to produce the recording of 60 pulses per second on the reference channel of the magnetic tape 35. At the same time, the output of the motor 22 is directed to the reference input of the differential mechanism 295 and is driving it at a speed which will operate the pulsing mechanism 439 at a rate to produce pulses for recording on the X channel of the tape at a frequency of 60 cycles per second. Therefore, in the absence of any other influence, the reference input to the differential mechanism 295 will cause the differential to operate the X pulsing mechanism at a rate to produce 60 pulses per second for recording on the tape and since the reference pulses are being produced by the pulsing mechanism 466 at the same frequency, there is correspondence so that the record calls for no motion along the X axis. In other words, the record indicates that the machine tool slide along the X axis is at rest. There must be a deviation in the frequency of the pulses on the X channel of the tape from the frequency of the pulses on the reference channel to produce slide motion on playback.

However, the frequency of the pulses produced by the mechanism 4301 may be varied by introducing the X component of the resolver 144 into the differential mechanism 295 to either add or subtract from the reference input into the differential 295, depending upon the direction of rotation of X input. An X input which subtracts from the reference input to the differential will cause the pulsing mechanism 430 to produce pulses at a frequency of less than 60 per second to indicate movement of X machineV tool slide yin one direction which may be termed the negative direction in the present description. Further- SB more, the greater the deviation of the frequency of the X pulses in a decreasing direction from the reference frequency of 6() cycles per second, the faster the machine tool slide will be caused to travel in the negative direction upon playback of the record.

On the other hand, if the X component of the resolver 144 is rotating in a direction to add to the reference input of the differential mechanism 295, the output of the differential 295 will drive the mechanical pulser 430 at a rate to produce pulses for recording on the magnetic tape at a frequency that is greater than the frequency of the reference pulses to call for a movement of the machine tool slide in the positive direction along the X axis. Under such circumstances, in the present embodiment, the X pulses will be recorded at a frequency greater than 60 cycles per second, and the greater the frequency of the X channel pulses above 60 cycles per second, the faster the machine tool slide will travel in the positive direction in response to the control produced by the record upon playback.

The specific construction of the apparatus is depicted in the drawings and reference is now made more particularly to FIG. 3 which illustrates the arrangement of the ball transmission 144. As previously mentioned, power for driving the apparatus is derived from the motor 22 which is mounted in the hollow base casting 21 with its shaft 8th extending in a horizontal plane. The motor shaft is provided with a bevel gear 81 which is disposed in meshing engagement with a bevel gear 82 secured to the lower end of a vertically extended primary drive shaft 83. The primary drive shaft 83 may be also rotated manually and to this end is provided with a bevel gear 84 which has meshing engagement with a bevel gear 86 secured to the end of a horizontally disposed shaft 87. The shaft 87 is journalled in a pair of antifriction bearings 88 and 89 and extends outwardly beyond the wall of the base casting 21. A handwheel 91 is rotatably mounted on an extending end 99 of the shaft 87 and may be manipulated for rotating the drive shaft 83. The handwheel 91 has a hub portion 92, the end of which is provided with a diametrical groove or slot 93 that is disposed to receive the outwardly extending ends of a pin 94 that is secured in the shaft 87 for establishing a driving connection between the handwheel 91 and the shaft 87. The handwheel 91 is arranged to be moved axially on the end of the shaft 87 into an engaged position, as shown in FIG. 3, wherein the pin 94 is engaged within the slot 93, or to a disengaged position. The manual rotation of the handwheel 91, when in the engaged position, serves to revolve the shaft 87 and thereby the primary drive shaft 83. It is therefore apparent that the primary drive shaft S3 may be power driven by the base motor 22 or may be manually rotated by means of the handwheel 91.

The primary drive shaft 83 extends upwardly through a bearing casting 97 which is disposed adjacent to the castings 23 and 24 and supported on the base casting 2,1. The primary drive shaft 83 continues upwardly through the transmission casting 27 to terminate in the cap or top casting 28 with its upper end being journalled therein. As shown in FIGS. 10 and l1, the upper end of the primary drive shaft 83 is provided with a gear 98 which is in meshing engagement with a gear 99 mounted on the upper end of a reference drive shaft 1419, shown in FIGS. 3 and l0. The primary drive shaft 83 is also connected to drive the capstan spindle 53, as shown in FIGS. 3 and l1, through the gear 99 which has meshing engagement with a gear 191 mounted on a vertical intermediate shaft 102 which is rotatably supported in the castings 27 and 28, being journalled therein by a pair of antifriction bearings 193 and 194. The lower portion of the intermediate shaft 192 is provided with a Worm 195 that has meshing engagement with the worm gear 54 which is secured to the inner extending end of the capstan spindle 53 as previously described.

aangaat The primary drive shaft 83 is also connected to drive the gear reduction transmission R1. As previously mentioned, the transmission R1 includes the change gear transmission 73 which in the structural embodiment, as shown in FIG. 3, comprises a pair of change gears 108 and 109. The change gear 108 is removably secured to the upwardly extending end of the intermediate shaft 102 and is in meshing engagement with the change gear 109. The change gear 109 is removably secured on a shaft 110 that is journalled in a pair of ball bearings 111 and 112 mounted in the top casting 28. The change gears 108 and 109 are accessibly disposed within a chamber 113 provided in a change gear housing 114 integrally formed with the cap or top casting 28 and they may be replaced' by other gears to vary the reduction ratio of the transmission R1 in well known manner. A removable cover plate 115 is provided to seal the chamber 113 and to provide access to the change gears 108 and 109.

The gear reduction transmission R1 also incorporates the infinitely variable speed changer 118 which is disposed within a suitable opening provided in the upper transmission casting 27 and arranged in a manner that a shaft 119 thereof, serving as an input shaft, extends upwardly into a socket 120 formed on the end of the shaft 110. The input shaft 119 of the speed changer 118 is rigidly coupled to the shaft 110 by means of a set screw` 121 which is threaded through the wall of the socket 120 to engage the shaft 119 to rigidly couple the two shafts together. An output shaft 122 of the speed changer 118 is displaced 180 from the shaft 119 and extends downwardly into the lower transmission casting 26. The in` put shaft 119 of the speed changer 118 is connected to drive its output shaft 122 at infinitely variable speed rates in a well known manner. The speed changer 118 includes an adjusting shaft 123 which is connected to effect an adjustment in the variable driving connection between the shafts 119 and 122 and operates, when actuated, to vary the speed change ratio between the input shaft 119 and the output shaft 122 within the limits of the mechanism.

The gear reduction transmission R1 includes fixed gearing 74, shown in FIG. 3, that comprises a gear 126 secured to the end of the output shaft 122 and which is in meshing engagement with a gear 127 that is fixedly secured to a shaft 128. The upper portion 129 of the shaft 128 is journalled in bearings 130 and 131 and the shaft extends downwardly therefrom through a bearing bracket 132 where it is journalled in a pair of antifriction bearings 133 and 134, the bracket 132 being secured to the exterior of the main casting 24. It is therefore apparent that the shaft 128 is rotated at a rate that will vary with a variation in the adjustment of the speed changer 118 as well as with a variation in the ratio of the change gears 73. The rotating .shaft 128 serves as a source of power for driving a mechanism to be subsequently dei scribed.

The upper portion 129 of the shaft 128 is provided with another gear 135 which is disposed to mesh with a gea 136 mounted on a shaft 137 journalled in the upper and lower transmission castings 27 and 26. The lower end 138 of the shaft 137 has secured to it a gear 139 having engagement with a gear 140. The gears 126, 127, 135, 136, 139 and 140 comprise the fixed gearing 74 referred to in the block diagram of FIG. 8 and which is connected to drive the ball transmission generally indicated in the diagrammatic view of FIG. 8 and in FIGS. 3 and ll by the reference numeral 144.

The ball transmission 144 is generally similar in construction and identical in operation to the ball transmission described in Patent No. 2,869,429 which issued on Ianuary 20, 1959. Its operation may be best understood from the diagrammatic view of FIG. 11 where only the principal parts of the mechanism are shown and are illustrated there schematically. The ball transmission 144 generally comprises a ball or sphere 175 which is supported for rotation about an infinite number of axes and is driven in its rotary movement by a drive wheel 161 which is in frictional driving engagement with the surface of the sphere. The drive wheel 161 is connected to be rotated about its own axis by the motor 22 through the transmission R1 and the rotation of the drive wheel 161 causes a rotation of the sphere 175 by virtue of the frictional engagement that the drive wheel 161 has with the sphere 175.

The rotating sphere 175 transmits power to a pair of power take-off wheels 188 and 189 that are likewise in frictional driving engagement with the sphere, the takeoff wheel 188 being located in a plane that is displaced from the plane of the take-off wheel 189. The takewheel 188 transmits the control information for the X axis of the machine tool slide motion while the take-off Wheel'189 transmits the control information for the Y axis of the slide motion.

In addition to being rotatable about its own axis, the drive wheel 161 is rotatable bodily to change the position of its axis of rotation and thereby change the position of the axis of rotation of the ball 175. An angular change in the position of the axis of rotation of the ball 175 produces a change in the distribution of the input between the two take-olf wheels 188 and 189. Thus, it is apparent that when the drive wheel 161 is revolved about its horizontal axis it will cause the ball 175 to revolve, and the axis of rotation of the ball 175 will be parallel to the axis of rotation of the drive wheel 161, this being true regardless of the position of the axis of the drive wheel 161. The power take-off wheels 188 and 189 being in frictional contact with the surface of the ball 175 will be driven with a peripheral speed equal to the surface speed of that part of the ball 175 that they are in contact with. Obviously, an angular change in the orientation of the axis of rotation of the ball 175 will change the peripheral speed of the surface of the ball that the take-off wheels 188 and 189 are in contact with, to change the rate of rotation of the take-off wheels, and this speed of the power take-off wheels will vary as the cosine of the angle that the axis of rotation of the ball 175 makes with the axis of the driven power take-off wheels 188 or 189.

The actual construction of the ball transmission 144 and the drive train for carrying power to the ball transmission 144 are best illustrated in FIG. 3. As previously mentioned, the power for rotating the drive wheel 161 to revolve the sphere 175 is derived from the motor 22 and transmitted to the gear transmission R1 which comprises the change gear transmission 73, the infinitely variable speed changer 118 and the fixed gearing 74. In order to effect the driving connection to rotate the drive wheel 161, the gear 140 of the fixed gearing 74 of the transmission R1 is secured to the upper portion of a planetary gear drive shaft 141 that extends downwardly into a planetary gear chamber 142 provided in the main casting 24. The drive shaft 141 is, in turn, connected to drive a planetary gear system generally denoted by the reference numeral 145.

The planetary gear system 145 is connected to rotate a shaft 157 that extends downwardly from the planetary gear system 145 into a housing 159 and has a bevel gear 158 secured to its lower end. The housing 159 serves to enclose a drive wheel gear train, generally denoted by the numeral 160, which transmits power to the drive wheel 161. The bevel gear 158 is connected to drive the gear train 160 and to this end has meshing engagement with a cooperating bevel gear 162 which is keyed to a stub shaft 163 that is journalled in the housing 159. A spur gear 166 is keyed to the extending hub of the bevel gear 162 and has meshing engagement with another spur gear 167. The spur gear 167 is integrally formed with a shaft 168 which is journalled in the housing 159 by a ball bearing 169 and extends outwardly therefrom into a hub 170 of the drive wheel 161. The shaft 168 is secured within the hub 170 by a pin 171 so that it will revolve in unison with 1 1 the drive wheel 161. The inner end of the hub 170 is also journalled in the housing 159 by a tapered roller bearing 172 so that the drive wheel 161 is freely rotatable about its axis within the housing 159.

The drive wheen 161, as previously mentioned, operates to rotate the sphere 175 which is retained in position and in frictional driving engagement with the drive wheel 161 by an idler wheel 176. The idler wheel 176 is in contact with the ball 175 at a point diametrically opposite the point of contact with the drive wheel 161 to retain the ball in driving engagement with the drive wheel.

The idler wheel 176 is rotatably mounted in a bracket 177 integrally formed on the upper portion of a shaft 178. The shaft 178 and the bracket 1'77 are rotatably mounted within a sleeve 179 by a pair of ball bearings 181 and 182 that are supported within the bore 25 of the main casting 24. The shaft 178 extends downwardly into the lower casting 23 and has secured to its lower end a gear cluster 183 which is fixed to the shaft 178 by means of a pin 184. Thus, the entire unit comprising the idler wheel 176, the bracket 177, the shaft 178 and the gear cluster 183, is supported within the bore of the casting 24 for rotation as a unit. Therefore, a rotary movement of the gear cluster 183 will produce a like rotary movement of the idler wheel 176. The drive wheel 161 will rotate in unison with the idler wheel 176 by reason of an interconnection between the gear cluster 183 and the housing 159 which rotatably supports the drive Wheel 161. Thus, the gear cluster 183 comprises two spur gears 273 and 274 with the latter being in mesh with a cooperating spur gear 275. The gear 275 is xedly secured to the lower end of a vertical shaft 276 that extends through a bore 277 formed in the main casting 24 and is journalled in a pair of ball bearings 278 and 279. A spur gear 281 is secured to the upper end of the shaft 276 and is in meshing engagement with a gear 192 formed at the lower end of the housing 159. As a result of this connection, rotation of the gear cluster 183 will cause a corresponding rotation of the housing 159, and the drive wheel 161 will rotate bodily with the housing 159 since it is supported thereby. The idler wheel 176 will likewise rotate bodily in unison with the drive wheel 161 by virtue of the fact that it is carried by the shaft 178 which also carries the gear cluster 183 and the idler wheel will therefore always be maintained in alignment with the drive wheel 161.

Such rotary movement or steering of the drive wheel 161 serves to change the angular position of its axis of rotation and the axis of rotation of the ball 175 varies accordingly to orient itself in a direction parallel to the axis of rotation of the drive wheel 161. The steering of the drive wheel 161 therefore serves to adjust the distribution of the input to the ball 175 between the two take-off wheels 188 and 189 with the distribution remaining in a sine-cosine relationship in which the speed of either of the take-off wheels 188 and 189 will vary as the cosine of the angle that the axis of rotation of the sphere 175 makes with the axis of the power take-off wheel. As previously mentioned, the steering of the drive wheel 161 is accomplished by power through the transmission Rs and to this end, the latter is drivingly connected to the gear 273 of the gear cluster 183 as will be subsequently described.

It is apparent from the above description that the drive wheel 161 is steered or rotated bodily by eecting a rotational movement of the entire housing 159 and its related parts. Since the bevel gear 162 is rotatably supported by the housing 159, when the latter pivots it moves the bevel gear 162 bodily with it about the bevel gear 158. Such bodily movement of the bevel gear 162 about the bevel gear 158 would normally affect the speed of rotation of the drive wheel 161, causing either a decrease or increase in its speed, depending on the direction in which the bevel gear 162 is moved. Such variation in the speed of the drive wheel 161 would adversely affect the accuracy of the input to the X and Y differential mechanisms.

Therefore, the bodily movement of the bevel gear 162 about its cooperating bevel gear 158 is compensated for by the operation of a planetary gear system 154 which is connected to the planetary gear system 145.

The planetary gear system 154 functions in response to the rotary movement of the housing 159 by reason of the action of a sun gear 194 which is mounted on an upwardly extending end of the housing 159 to be located in position to form a part of the planetary gear system 154. Therefore, the sun gear 194 will rotate with the housing 159 to actuate the planetary gear system 154 when the drive wheel 161 is steered to adjust the distribution of the output of the ball'transmission 144. The planetary gear system 154, in turn, is connected by a double fiange collar 151 to the planetary gear system 145 which transmits the drive for rotating the drive wheel 161 about its own axis. As a result, the actuation of the planetary gear system 154 by rotation of the sun gear 194 affects the planetary gear system to compensate for the bodily movement of the bevel gear 162 about the bevel gear 158 by either decreasing 4or increasing the rotation of the shaft 157, depending upon the direction in which the rotation of the drive wheel 161 and its associated housing 159 occurs.

Thus, if the steering of the drive wheel 161 causes bodily movement of the bevel gear 162 about the bevel gear 158 to produce a decrease in the speed of the drive wheel 161, the rotational movement of the housing 159 would cause an increase in the speed of the bevel gear 158 through the planetary gear systems 145 and 154 as described, so that the rate of rotation of the drive wheel 161 will remain substantially constant. In like manner, if steering of the drive wheel 161 causes the bevel gear 162 to be moved bodily about the bevel gear 158 in a direction to produce an increase in the speed of the driving wheel 161, the planetary gear systems 145 and 154 will act to decrease the speed of the bevel gear 158 a sufficient amount to compensate the bodily movement of the bevel gear 162, and thereby preserve the uniformity of the rotation of the drive wheel 161. A more detailed description of the construction and operation of this compensating mechanism in the gear train to the drive wheel 161 is contained in the previously mentioned Patent No. 2,869,429.

As stated the steering of the drive wheel 161 is accomplished by means of the steering transmission Rs which is indicated diagrammatically in FIG. 8. An exemplary embodiment of the steering transmission Rs is shown in FIGS. 3 and ll and as there shown, it comprises a gear 210 keyed or otherwise secured to the drive shaft 141 for rotation with it for taking power from the shaft 141 for effecting the steering of the drive wheel 161. The `steering transmission is therefore driven by the shaft 141 which also is connected to drive the planetary gear system for rotating the drive wheel 161 about its own axis to constitute the input to the ball transmission 144.

The gear 210 is in meshing engagement with a power transmitting gear 211 fixed to a power transmitting shaft 212 rotatably journalled in a pair of bearings 213 and 214 mounted in the upper and lower transmission castings 27 and 26, respectively. A gear 215 fixedly secured to the power transmitting shaft 212 is in meshing engagement with a gear 216 secured to a rotatable shifter shaft 217. The shifter shaft 217 extends upwardly through a bore 218 to protrude through a boss 219 integrally formed on the cap or top casting 28. The shifter shaft 217 is provided with a knob 221i by which the shifter shaft may be manually actuated axially to a selected one of three positions. The gear 216 is disposed in meshing engagement with an idler gear 221 fixed to an idler shaft 222 journalled in the lower transmission casting 26. The idler gear 221 has meshing engagement with another idler gear 223 fixedly secured to a shaft 224 journalled in the upper and lower transmission castings 27 and 26. The shaft 224 operates to rotate a gear 226 fixed to the shaft 224 for rotation with it. The gear 226 is disposed in meshing engagement with a gear 227 ixedly secured to a shaft 228 which extends upwardly into a change gear chamber 229 formed in the boss 219, being journalled in the upper transmission casting 27 in a bearing 230 and a pair of ball bearings 231 and 232. The chamber 229 contains the change gearing 75 which comprises a change gear 233 removably secured to the extending end of the shaft 228 and is disposed in meshing engagement with a change gear 236 removably secured to the extending end of an extension shaft 237 extending downwardly from the change gear chamber 229 into the cap or top casting 28, being journalled therein by a pair of ball bearings 238 and 239.

` An infinitely variable speed changer, generally indicated by the reference numeral 242, is disposed within a bore 243 provided in the upper transmission casting 27 and arranged in a manner so that its input shaft 244 extends upwardly into a socket 245 formed at the lower extremity of the extension shaft 237 and is rigidly coupled thereto by means of a set screw 246. An output shaft 247 of the speed changer 242 extends downwardly into the lower transmission casting 26 into a socket 248 which is formed on the upper end of an extension shaft 249 that is journalled in a bearing 251 mounted in the main casting 24. The output shaft 247 and the extension shaft 249 are rigidly coupled together by means of a set screw 252 which is threaded into the socket 248 to engage the periphery of the output shaft 247. The infinitely Variable speed changer 242 is an exact duplicate of the speed changer 118 and operates in the same manner. An adjusting shaft 253 is provided for the speed changer 242 and operates when actuated to vary the speed change ratio of the speed changer 242 within the limits of the mechanism.

The drive from the speed changer 242 is transmitted from the shaft extension 249 to a pinion gear 254 mounted on the lower end of the shaft extension 249 for rotation therewith. As shown in FIGS. and 1l, the pinion gear 254 is in meshing engagement with an intermediate transmission gear 255 fixedly secured to a vertically disposed stub shaft 256 journalled in the lower transmission casting 26 and the main casting 24. The stub shaft 256 has secured to its lower end a pinion gear 257 which is disposed to mesh with a gear 258, as shown in FIGS. 3 and 5. The gear 258 is mounted on the upper end of a steering adjusting shaft 260 which extends downwardly into the base casting 21, being journalled in bearings 261, 262 and 263. The adjusting shaft 260 is connected to drive a fixed gear transmission, generally indicated by the reference numeral 265, its lower end being provided with a pinion gear 266 that is secured to it for rotation with it. The pinion gear 266 is disposed in meshing engagement with a gear 267 integrally formed on a pinion shaft 268, journalled in a pair of antifriction bearings 269 and 271. The upper end of the pinion shaft 268 has an integrally formed pinion 272 which operates to drive the gear cluster 183 fixedly secured on the end of the ball loading wheel shaft 178. The gear cluster 183 includes the gear 273 in mesh with the pinion 272 and the pinion 274 drivingly enga-ged with the spur gear 275. The drive for steering the drive wheel 161 is then completed as previously described through the shaft 276, the gear 281 and the gear 192 which is mounted on the lower end of the housing 159.

In order to steer the drive wheel 161 in a reverse or counterclockwise direction a reversing drive is provided. To this end, the shifter shaft 217 is provided with a fixed gear 283 that is secured thereto for rotation and axial movement with the shaft. Upon movement of the shifter shaft 217 to its uppermost position the gear 283 kwill be moved upwardly into meshing engagement with the gear 226, while the gear 216 is moved upwardly out of engagement with the gears 215 and 221, to disconnect the forward or clockwise steering drive from the drive shaft 141 to the drive wheel 161. As the gear 216 is moved out of engagement with the gears 215 and 221, upon movement of the shifter shaft 217 to its uppermost position, the gear 216 will be moved into engagement with a drivin-g gear 284 fixedly secured to the intermediate shaft 212. Thus, a drive in a reverse direction will be established from the drive shaft 141 and the gear 210, to the gear 211 on the intermediate shaft 212 and through the shaft 212 to the gear 284. From the gear 284 the drive will continue through the gear 216 and the shifter shaft 217 to the gear 283 and thence to the gear 226 and be transmitted through the balance of the transmission previously described, to effect counterclockwise steering of the drive wheel 161.

In order to establish the proper location of the shifter shaft 217 for any one of its three positions, namely, reverse or counterclockwise steering, neutral or no steering, and forward or clockwise steering, the upper portion 285 of the shifter shaft 217 is provided with three annular notches or grooves 286, 287 and 288. The notches or grooves 286, 287 and 288 are adapted to receive a detent ball 289 which is mounted in a horizontally disposed bore 291, provided in the extending boss 219 through which the shifter shaft 217 extends. The detent ball 289 is resiliently urged inwardly towards the shifter shaft 217 by means of a spring 292 retained within the bore 291 by means of a set screw 293. Thus, with the shifter shaft 217 positioned as shown in FIG. 3, the annular groove 286 is in position to receive the detent ball 289 which operates to maintain the shaft 217 in position. When the shifter shaft 217 is in its lowermost position, wherein the annular groove 286 is in position to receive the detent ball 289, it engages the transmission so as to effect clockwise steering of the drive wheel 161. In this position the gear 283 is disengaged from the gear 226 and the gear 216 is disengaged from the drive gear 284 but is positioned to engage the clockwise drive gear 215.

To effect counterclockwise steering of the drive wheel 161, the shifter shaft 217 is moved upwardly, by means of the knob 220, so as to align the annular groove 288 in position to receive the detent ball 289. In this position the gear 283 will be moved into meshing engagement with gear 226, and the gear 216 will be disengaged from the idler gear 221 and the clockwise drive gear 215 and engaged with the counterclockwise drive gear 284. If it is desired to maintain the axis of the drive wheel 161 in a fixed or stationary position, the shifter shaft 217 may be moved to an intermediate position wherein the annular groove 287 is positioned to receive the detent ball 289. In this position the gear 283 will move upwardly, as viewed in FIG. 3, with the shifter shaft 217, but will not be engaged with the gear 226. Simultaneously, the gear 216 will be moved out of engagement with the idler gear 221 and the clockwise drive gear 215 into an intermediate position between the counterclockwise drive gear 234 and the clockwise drive gear 215. Thus, the drive from the drive shaft 141 to the steering gear 192 is interrupted and the axis of the drive wheel 161 will be maintained stationary.

In order to eliminate lost motion in the gear train for transmitting the torque to steer the drive wheel 161 a pair of torque motors 300 and 301 are connected in the gear train to act in opposition to each other, as shown in FIGS. 5 and l1, for removing backlash from the gear train. To this end, the torque motor 300 is supported within a housing 302 integrally formed with the main casting 24, being connected to drive a gear 303. The gear 303 is disposed in meshing engagement with an idler gear 304 which is arranged so as to extend into the bore 25 of the main casting 24 through a suitable opening 305, into meshing engagement with a gear 306. The gear 306 is mounted about the upper end of the housing 159, as shown in FIG. 3, and is supported in position on an annular flange 307 integrally formed on the housing 159, being secured thereto by means of a dowel `(not shown) in a well known manner. The torque motor 301, acts to apply a yieldable force in the transmission in a direction opposite to the direction in which the torque motor 380 acts and is mounted in a housing 308, being connected to drive a gear 389 rotatably supported on a shaft 3111 journalled in the housing 308. The gear 309 is in meshing engagement with the gear 255 to thereby preload the transmission which transmits the drive to the steering gear 192 as previously described. Thus, the housing 159, in which the driving wheel 161 is rotatably supported is urged in one direction by the torque motor 301) to produce a yieldable force in the transmission while the torque motor 301 is producing a similar force in the same transmission but acting in the opposite direction. As a result, the torque motors 300 and 301 operate to eliminate lost motion regardless of the direction of steering so that the driving wheel 161 and its loading wheel 176 will respond instantaneously to effect a desired distribution of the output of the resolver 144.

Power steering of the drive wheel 161 through the transmission Es is provided for recording information which will control the machine tool slides to produce a curvilinear configuration in the workpiece. Under these circumstances it is necessary to continuously steer the drive wheel 161 while it is rotating about its own axis so that on playback, the rate of travel of one of the machine tool slides will be accelerating at a predetermined rate while the other slide will be decelerating to produce the curvilinear conguration. The radius of such curvature, of course, will vary with the rate at which the drive wheel 161'is steered, with the radius decreasing as the rate of steering is increased and vice versa.

For this reason, the speed changer 242 is incorporated in the transmission Rs to provide a convenient means of adjusting the rate of the steering action for obtaining the desired radius of curvature. Since the speed changer 242 is a part of the transmission Rs, an adjustment of the speed ratio of the speed changer 242 will vary the ratio of the transmission Rs to either increase or decrease the rate of steering of the drive wheel 161 to establish the desired radius of curvature. To effect an adjustment of the speed changer 242 an adjusting knob 475, shown in FIGS. 2, 9 and l0, is provided and is secured to the outwardly extending end of a horizontally disposed actuating shaft 476 rotatably supported in the upper transmission casting 27. The inner end of the shaft 476 is provided with a bevel gear 477 which is in meshing engagement with a bevel gear 478 provided on the end of the speed changer adjusting shaft 253.

Rotation of the knob 475 will operate to effect an adjustment of the speed changer 242, which, in turn, will operate to rotate a shaft 479 operably connected therein. The shaft 479 extends outwardly from the speed changer 242 through the upper transmission casting 27 and extends through an indicator gear box 480 secured to the side of the casting 27. The outwardly extending end 481 of the shaft 479 is provided with a dial 482 having a series of unit indicia readable against an indicator mark (not shown). The unit indicia on the dial 482 indicate the rate of steering established by the operation of the knob 475. Since the indicia on the dial 482 are in full units and the speed changer 242 is infinitely variable within its limits, other indicia bearing dials 487 and 488 with appropriate reduction gearing 490 are provided to enable the speed changer to be adjusted to a desired thousandth of a unit.

Since the setting of the dials indicate only a particular setting of the speed changer 252, a chart (not shown) is provided on which a comparable radius in inches is given for the dial settings. Thus, if it is desired to record on the magnetic tape a path of travel about a radius of ve inches it is only necessary to refer to the chart (not shown) and note the dial settings given for a tive inch radius. The knob 475 will then be turned in one direction or the other, as the case may be, until the dials indicate the setting indicated by the chart. In this manner proper steering of the drive wheel 161 will be accomplished so that proper distribution of take-off speeds will be effected to vary the motion input from the sphere 175 to the X and Y take-off wheels 188 and 189 in a sine-cosine relationship.

As previously mentioned the output of the sine-cosine resolver 144 is along X and Y axes which feed separate X and Y differential mechanisms generally indicated by the reference numerals 295 and 296 respectively, as shown diagrammatically in FIG. 1l. The output from the resolver 144 is transmitted to the separate X and Y differentials 295 and 296 through separate transmissions, the transmission to the X differential being represented in the diagrammatic view of FIG. 8 by the block R0. To this end, as shown in FIGS. l and 4, the X and Y power take-off wheels 188 and 189, respectively, are rotatably supported within housings 315 and 316 in frictional engagement with the sphere 175 with their axes of rotation in the same horizontal plane but disposed apart relative to each other. The frictional driving engagement of the take-off wheels 188 and 189 with the sphere is maintained through a pair of reaction or loading wheels 317 and 318, respectively. The loading wheels 317 and 318 are in contact with the sphere 175 at points diametrically opposite the point of contact with their respective take-oif wheels, to maintain the sphere in driving engagement with the take-oft" wheels. Since each of the take-off wheels 188 and 189, their associated loading wheels, and associated drive mechanism are exactly the same, a detailed description of the X power takeoff wheel 188 only will be given, and the description thereof will apply to the Y power take-olf wheel 189 and its associated mechanism.

As shown in FIGS. 4 and 6, the X power take-off wheel 188 is rotatably mounted on an X power take-off shaft 319 which extends outwardly of the housing 315 into an X differential support, generally identified by the reference numeral 321, being journalled in a pair of axially adjustable antifriction bearings 323 and 324. The power take-off wheel 188 is provided with extending hubs 320 and 322 which are journalled in a pair of radial antifriction bearings 325 and 326, carried in the housing 315. Thus, the shaft 319 floats within its bearings 323 and 324 and is freely rotatable relative to the wheel 188, while the wheel 188 is freely rotatable relative to the shaft 319 but is maintained axially stationary. To effect a clutching of the shaft 319 to the wheel 188 in order to effect a drive therebetween, the end of the shaft 319, in the housing 31S, is provided with a threaded end 327 which threadedly receives a knurled nut 328. When the nut 328 is threaded onto the shaft 319 and into engagement with the axial face of the hub 328 it will effect axial movement of the shaft 319 leftwardly, as viewed in FIGS. 4 and 6. Since the wheel 188 cannot move axially, movement of the shaft to the left will operate to positively engage a shoulder 329 on the shaft 319 with the axial face of the hub 322 of the wheel 188 to effect a driving engagement of the wheel 188 with the shaft 319.

The loading wheel 317, associated with the power takeoff wheel 188 is rotatably supported in a bracket 331 formed on the inner end of a carrier 332. The carrier 332 is supported within a horizontal bore 333 provided in the main casting 24 and is urged inwardly to effect engagement of the loading wheel 317 with the surface of the sphere 175. To positively engage the sphere 175 With the power take-off wheel 188 the loading wheel 317 is firmly engaged with the sphere 175 by means of a compression spring 334. The spring 334 is mounted within the bore 333 and positioned so as to engage the outer end of the carrier 332. A retainer cap 335 is inserted within the bore 333 into engagement with the end of the spring 334 and is secured in position by means of screws 336. The retainer cap 335 operates to compress the spring 334 17 to effect a desired loading of the wheel 317 against the Surface of the sphere 175 and thereby effect the desired frictional engagement of the sphere 175 with the power take-off wheel 188.

To eect an exact alignment of the loading wheel 317 relative to its associated power take-off wheel 188 and to prevent the carrier 332 and thereby the loading wheel 317 from rotating within the bore 333 whenever the rotational axis of the sphere 175 is varied, the carrier 332 is connected to the fixed retainer cap 335. To this end, a pair of dowels 337 are inserted through suitable openings 338 and 339 provided in the retainer cap 335, and are received in openings 340 and 341 provided in the carrier 332. Thus, the carrier 332 and thereby the loading wheel 317 are axially movable within the bore 333 to effect the desired frictional engagement of the wheel 317 with the sphere and thereby maintain the proper frictional engagement of the sphere 175 with the take-off wheel 188. However, the loading wheel 317 will be maintained in alignment with the power take-off wheel 188 by operation of the dowels 337 connected to the retainer cap 335 which is screw fastened in on oriented position to the main casting 24.

Similarly, the Y power take-off wheel 189 is rotatably mounted on a Y drive shaft 342 one end of which extends within the housing 316 being journalled therein in an axially adjustable bearing 343. The opposite end of the shaft 342 extends through a Y differential support, generally indicated by the reference numeral 344, being rotatably supported therein by an axially adjustable bearing 345. The Y power take-off wheel 189 is similar to the take-off wheel 188, being journalled in a pair of antifriction bearings 346 and 347. Thus, the power take-off wheel 189 is freely rotatable on the shaft 342 while the shaft 342 is rotatable in its bearings 343 and 345. The shaft 342 is provided with a threaded end 348 which receives a clutching nut 349 that operates to engage the shaft 342 with the power take-off wheel 189, as described in conjunction with the wheel 188 and shaft 319.

The shafts 319 and 342 are each connected to drive a respective transmission, one of which is indicated in the block diagram of FIG. 8 as Ro. The transmission Ro comprises a change gear generally identified by the reference numeral 356, and fixed gearing generally identified by the reference numeral 76, as indicated diagrammatically in FIG. 8. Each of these transmissions are connected to one side of respective X and Y differential mechanisms.

As shown in FIGS. 4, 6 .and 7 and diagrammatically in FIG. ll, the shaft 319 extends through the X differential s-upport 321 with the extending end 355 thereof having the change gear 356 mounted thereon for rotation with it. The change gear 356 is adapted to drive a fixed gear 357 through a positionable or clutching gear 358. The gear 357 is pinned to the extending end 359 of a shaft 360, journalled in a pair of antifriction bearings 361 and 362 supported in the differential support 32.1. The clutching gear 358 is also employed to transmit a drive fro-m a sine-cosine transmission to be described and generally indicated by the reference numeral 370, to the X differential mechanism 295. When so employed, the clutching gear 358 must be disconnected from the change gear 356 to interrupt the X output drive from the sphere 175 to the differential 295. In either condition of operation the clutching gear 358 lmust be positively retained in meshing engagement with the fixed gear 357. Therefore, as best shown in FIG, 7, the clutching gear 358 is affixed to a rtatable shaft 363 journalled in one end of a pivotal arm 364. The arm 364 is pivotally secured at its opposite end to the extending end 359 of the shaft 360 being secured thereon by a snap ring 365. To maintain the clutching gear 358 in meshing engagement with the fixed gear 356 to thereby effect a drive to the gear 357 a spring 366 is provided. The spring 366 is connected to the extending end of a stud 367 carried by the pivotable arm 364 with its opposite end being connected to a stud 368 carried by the outer wall of the different-ial support 321 in position above the fixed gead 356. Thus, the force exerted by the spring 366 maintains the clutching gear 358 in meshing engagement with the change gear 356 to thereby effect a drive from the gear 356 through the clutching gear 358 to the fixed gear 357.

The gear 357 effects a reduction drive to one side of the X differential mechanism 295 through a fixed gear transmission carried in the differential support 321. To this end, as shown in FIGS. 6 and 1l, the inner end of the shaft 360 is provided with a gear 371 which is secured thereto for rotation with the shaft. The gear 371 is in meshing engagement with a gear 372 integrally formed on a shaft 373 which is rotatably supported by a pair of antifriction bearings 374 and 375 mounted in a wall 376 of the differential support 321 and a bearing support plate 377, respectively. The bearing support plate 377 is secured to the wall 376 by cap screws 378. A pinion 379 integrally formed with the shaft 373 is in meshing engagement with a gear 380 integrally formed with a shaft 381 which is journalled in a pair of antifriction bearings 382 and 383 carried in the plate 377 and the wall 376, respectively. A pinion 384 integrally formed on the shaft 381 is in meshing engagement with a driving gear 385 mounted on and secured to the hub of an input bevel gear 386 of the X differential mechanism 295. The driving gear 385 operates to drive the bevel gear 386 which is mounted for free rotation on a pulser drive shaft 387 journalled in a pair of antifriction bearings 388 and 389 carried in suitable openings in the walls of the differential support 321. Thus, the output of the Sphere 175 along the X axis is transmitted to the X differential mechanism 295 through the change gear 356, the fixed gearing 358, 357, 371, 372, 379, 380, 384, and 385 and the differential input bevel gear 3.86 to the pulser shaft 387 with a reduction of 25 to 1 being effected.

Similarly, the output of the sphere 175 along the Y axis is transmitted to the Y differential mechanism 296 from the take-off wheel 189, as shown diagrammatically in FIG. 11, through an identical reduction transmission comprising a change gear 395, a clutching gear 396 and fixed gearing 397, 398, 399, 400, 405, 401 and 402 which is connected to drive an input bevel gear 403 of the Y differential mechanism 296. The Y reduction transmission is identical in construction to the X reduction transmission, previously described in detail, with the clutch gear 396 being rotatably supported at the end of a pivotal arm 404, as shown in FIG. 1, and held in meshing engagement with the gear 395 by a spring 406 operating as does the spring 366.

From the diagrammatic illustration in FIG. 11 it can be readily observed how the steering of the drive wheel 161 effects the distribution of the power between the X and Y power take-off wheels 188 and 189, respectively. With the drive wheel 161 in the position shown in FIG. l1, the axis of rotation of the sphere 175 is parallel to the axis of rotation of the X power takeoff wheel 188, and to the axis of rotation of the Y power take-off wheel 189. In this position the X takeoff wheel 188 is contacting the sphere 175 at a point of maximum surface speed of the sphere 175, while the Y power take-off wheel 189 is contacting the sphere at a point of no surface speed. With the elements in this position, the take-off wheel 188 is being driven at maximum speed, and the take-off wheel 189 is stationary. Therefore, the input bevel gear 386 of the X differential mechanism 295 is being rotated at a maximum rate, while the input bevel gear 403 of the Y differential mechanism 296 is maintained stationary.

If the drive wheel 161 were `steered to a position 90 from the position shown, it would be located in the same plane as the Y power take-off Wheel 189. In this position, the take-off wheel 189 would be driven at maximum speed, while the X power take-off wheel 188 would be stationary. The bevel gear 403 of the Y differential 19 mechanism 296 would then be driven at maximum rate, while the bevel gear 386 of the X differential mechanism 295 would be maintained stationary.

On the other hand, if the drive wheel 161 were steered to a position 45 from the position shown in FIG. l1, it would be at an angle midway between the planes of the power take-off wheels 188 and 189. In this position the surface speed of the sphere 175 at the points of contact with the power take-off wheels 18S and 189 would be equal and both take-01T wheels would be driven at the same rate. Under this condition, the input bevel gears 386 andA 403 of the respective differential mechanisms 295 and 296 would be rotating at equal speeds and the input to both differential mechanisms from the sinecosine resolver would be the same.

Thus, it can be seen that as the axis of rotation of the sphere 175 is changed by steering the drive wheel 161, the distribution of the take-oft' speed from the sphere 175 to the X and Y power take-off wheels 188 and 189 is changed accordingly, to vary the motion input from the sphere to the respective X and Y differential mechanisms 295 and 296, respectively. The input to the X and Y differential mechanisms 295 and 296 always remains in a sine-cosine relationship regardless of the direction in which the drive Wheel 161 is steered.

Therefore, as the drive wheel 161 is steered, the rate of rotation of one of the components of the ball transmission 144 will be increased while the other will be decreased in a sine-cosine relationship. The pulses produced by the rotation of these two components will, of course, vary in frequency accordingly. In view of the sine-cosine relationship between these two components they may be adjusted by steering the drive wheel 161 to produce pulses for recording on the X and Y channels of the magnetic tape at frequencies which, on playback, will cause the two machine tool slides to travel along the X and Y axes at rates to produce any desired resultant movement between the X and Y axes.

Thus, with reference tothe above mentioned examples of the angular positions of the drive wheel 161, if the latter is steered to the position shown in FIG. l1, the X take-off wheel 188 is driven at maximum speed in a positive direction and the Y take-off wheel 189 is stationary. This produces pulses at maximum frequency for recording on the X channel of the tape to produce a maximum rate of travel of the machine tool slide along the X axis on playback while the pulses on the Y channel call for the machine tool slide along the Y axis to remain at rest. The motion is therefore parallel with the X axis in a positive direction.

If the drive wheel 161 were steered in a counterclockwise direction as viewed from the top to a position 90 from the position shown in FIG. 1l, it would be located in the same plane as the Y power take-off wheel 189 to rotate the latter at a maximum rate in a positive direction and the X take-olf wheel 188 would be stationary. This produces pulses at maximum frequency for recording on the Y channel of the tape to produce a maximum rate vof travel of the machine tool slide along the Y axis onplayback, while the pulses on the X channel call for the machine tool slide along the X axis to remain at rest. The motion would therefore be parallel to the Y axis in a positive direction.

On the other hand, if the drive wheel 161 were steered in a counterclockwise direction as viewed from the top to a position 45 from the position shown in FIG. 11, as previously mentioned, both take-off wheels would be driven at the same rate in a positive direction. The pulses would then be recorded on both the X and Y channels of the magnetic tape at the same frequency but at a greater frequency than the reference frequency to indicate the positive direction. On playback, the pulses on the X and Y channels of the magnetic tape would ycause `movement of the two machine tool slides along the X and Y axes at the same rate of travel to produce a resultant movement at 45 to the X and Y axes in a positive direction. It is therefore apparent, that by steering the drive wheel 161 the frequencis of the pulses on the X and Y channels may be infinitely varied without deviating from the sine-cosine relationship to cause the two machine tool slides to move along the X and Y axes respectively at varied rates of travel in a sine-cosine relationship with respect to each other to produce any desired resultant movement.

If the drive wheel 161 were steered 135 from the position shown in FIG. 11, in a counterclockwise direction as viewed from the top, the Y take-off wheel 189 would continue to be rotated in a positive direction but the direction of the X take-off wheel 188 would be reversed to rotate it in a negative direction. Therefore, the resultant motion of the machine tool slides, on playback of the record, would be displaced from the position of the resultant movement produced when the drive wheel 161 was located 45 in a counterclockwise direction from the position shown in FIG. 11.

As previously mentioned, the output of the sine-cosine resolver to the X and Y differential mechanisms 295 and 296 is related to a reference output which is obtained from the common motor 22 connected through separate but identical gear transmissions to an opposite input bevel gear of the respective X and Y differential mechanisms 295 and 296. The reference drives to the differential mechanisms 295 and 296 are taken from the reference drive shaft 100, which as previously described is driven by the motor 22 at a constant rate by reason of its driving connection to the primary drive shaft 83 through the gears 98 and 99. As shown in FIGS. 3, 5, 7 and l0, and diagrammatically in FIG. 11, the reference drive shaft 100 extends downwardly from the top casting 28 and is connected by a coupling 411 to the outwardly extending end of a bevel gear shaft 412 which is journalled in the bearing casting 97 by a pair of antifriction bearings 413 and 414. A bevel gear 415 integrally formed on the lower end of the shaft 412 is disposed in meshing engagement with a pair of bevel gears 416 and 417. The bevel gear 416 is integrally formed on the end of a shaft 418 which is journalled in the bearing casting 97 by a pair of antifriction bearings 419 and 421. The bevel gear 417 is likewise, integrally formed on the end of a shaft 422,.shown in FIGS. 3, 4 and 5, which is also journalled in the bearing casting 97, but is disposed 90 from the shaft 418. The shafts 418 and 422 transmit the drive from the reference drive shaft 100 to separate gear transmissions which operate to effect a reference input to the X and Y differential mechanisms 295 and 296, as previously mentioned.

To effect a reference input to the X differential mechanism 295, the shaft 418 has secured to its outwardly extending end a gear 423 which has meshing engagement with a gear 424. The gear 424 is secured to a shaft 425 journalled in the differential support 321 and is disposed in driving engagement with a gear 426, shown in FIGS. 6 and 7 and diagrammatically in FIG. l1, that is secured to the hub of a differential input bevel gear 427, as shown in FIG. 6, and which is of the same size and with the same number of teeth as the bevel gear 386, both of which are a part of thedifferential mechanism 295. The differential input bevel gear is mounted for free rotation on the pulser drive shaft 387. Thus, the X differential mechanism 295 receives the output of the sphere from the Xtake-off wheel 188 which operates to drive the inputbevel gear 386, and also receives the output of the reference drive through the input bevel gear 427.

These outputs are then summed by the differential mechanism 295 into a resulting output which is transmitted to an X mechanical pulser mechanism, generally indicated by the reference numeral 430. To this end, a bevel gear 431 is disposed in meshing engagement with both input bevel gears 386 and 427 and is rotatably mounted on a stub shaft 432 which is fxedly supported 21 in a carrier 433. The carrier 433 is mounted on the pulser shaft 387 and secured thereto by means of a set screw 434 so as to effect rotation of the pulser shaft. Since the input bevel gears 386 and 427 are freely rotatable relative to the pulser shaft 387, they will operate to drive the bevel gear 431 bodily in an orbital path of movement. With the bevel gear 431 being supported by the carrier 433 which is secured to the pulser shaft 387, bodily orbital movement of the bevel gear 431 will operate to drive the pulser shaft at a rate which is onehalf the algebraic sum of the rate of rotation of the two separate motions of the bevel gears 386 and 427. The gear ratios of the drives to the differential mechanism 295 are arranged to accommodate the differential mechanism 295 so that its output will drive the X pulser mechanism 430 at a rate which is related to the rate of operation of the reference pulser mechanism 460 in such a manner that the pulses produced by the two pulser mechanisms may be compared on playback of the record for regulating the operation of the X machine tool slide.

The output of' the pulser shaft 387 is employed to mechanically operate the pulser mechanism 430 for actuating the electronic fiip-op circuit 78 as previously described in connection with FIG. 8 to change the state of the flip-flop for producing the pulses which are recorded on the magnetic tape. The electronic flip-flop is electrically connected to a section or channel of the recording head 44 which operat-es, upon the change in the state of the Hip-flop, to impress a change of polarity upon the magnetic tape passing over it so that alternate south and north poles are impressed upon the magnetic tape by operation of the flip-flop circuit with each change in polarity constituting one of the pulses previously referred to, the frequency of the pulses depending upon the rate of the output of the differential mechanism. The pulser mechanism 430 is driven by the pulser shaft 387 which extends outwardly of the differential support 321 and has secured thereto for rotation with it a cam disc or plate 435. As clearly shown in FIG. 7, the disc 435 is provided with a cam 436 which is arranged to open the contacts of a pair of normally closed switches, generally indicated by the reference numerals 437 and 438. The normally closed switches 437 and 438 are carried on the outer face of the differential support 321 and are positioned 180 apart, the two switches 437 and 438 being identical in construction.

As shown, the switch 437 comprises an arm 439 of a nonconducting material which is pivotally mounted on a bracket 440 secured to the front face of the differential support 321. The arm 439 extends downwardly into the path of travel of the cam 436 so that the face of the cam in moving through its circular path of travel in a clockwise direction will engage the end of the arm to move it rightwardly, as viewed in FIG. 7. The arm 439 is provided with an electrically conductive contact 441 which is adjustably secured therein in position to engage an electrically conductive stationary contact 442. The contact 442 is adjustably mounted in a nonconducting bracket 443 that is secured to the outer face of the differential support 321. To maintain the contact 441 in engagement with the contact 442 a spring 444 is provided. The spring 444 has one of its ends connected to the arm 439 while its opposite end is connected to a post 445 which extends outwardly from the differential support 321. The arrangement is such that when the cam 436 of the disc 435 is rotating in a clockwise direction it will engage the end of the arm 439 to effect a momentary separation between the contact 441 and the contact 442. Thus, the output of the X differential mechanism operates to rotate the disc 435 which in turn opens the normally closed switches 437 and 438 once in each revolution of the disc 435. `When the switch 437 is opened, it effects a change in the state of its associated electronic flip-nop circuit 78 which is shown schematically in FIG.

animar' 8, to cause the flip-flop circuit to impress a magnetic pole of positive polarity on the magnetic tape that is moving over the recording head 44 by operation of the capstan 58. Similarly, when the switch 438 is opened it effects a change of state in the electronic ip-op circuit 78 so that it resumes its original state and in doing so impresses a negative magnetic pole on th-e magnetic tape. These magnetic poles which are impressed upon the magnetic tape in response to the rotation of the take-off wheel 188 are recorded on a channel of the magnetic tape, referred to as the X channel, and each change in the polarity on the magnetic tape constitutes a pulse.

Similarly, to effect a reference input to the Y differential mechanism 296, as shown in FIG. 5 and diagrammat-ically in FIG. ll, the shaft 422 is provided with a gear 449 which is secured thereto for rotation with it. The gear 449 is disposed to drive a gear 450 that is mounted on :a shaft (not shown) journalled in the Y differential support 344. The gear 450, in turn, operates to drive a gear 451 which is secured to the hub of a Y differential reference input bevel gear 452, shown in FIGS. l and l1, which is supported on a Y pulser shaft 453 for rotation relative to it, with the pulser shaft 453 being rotatably supported in the Y differential support 344. It is therefore apparent that the construction of the Y reference drive transmission is identical to the arrangement and construction of the X reference drive transmission, previously described in detail.

The Y differential mechanism 296, as shown in FIGA l and diagrammatically in FIG. 11, receives the output of the sphere from the Y power take-off wheel 189 which is connected to drive the input bevel gear 403 and also receives the output of the reference drive through the input bevel gear 452. These outputs are resolved, by the Y differential mechanism 296, into a resulting output which is transmitted by the rotating Y pulser shaft 453 to rotate a Y pulser disc 455. As shown in FIG. l and diagrammatically in FIG. 11, the pulser disc 455 is secured to the extending end of the pulser shaft 453 and is provided with a cam 456 which operates upon rotation of the disc 455 to open a pair of normally closed switches (not shown) which are identical to the switches 437 and 438 associated with the X mechanical pulser 430. The switches (not shown) associated with the Y differential pulser, when actuated to an open condition, effect a change in the state of an associated Y channel electronic fii-p-flop (not shown) which is identical to the flip-flop circuit 78 for the X axis of slide motion. The Y channel flip-flop (not shown) is connected to another section of the recording head 44 and is actuated by the switches to impress magnetic poles of alternately positive and negative polarity on a Y channel of the magnetic tape.

As previously described in connection with the diagrammatic View of FIG. 8, alternate north and south magnetic poles, or pulses, are also recorded on a reference channel of the magnetic tape which is independent of the X and Y channels of the tape. However, while the X and Y pulses occur at a varying frequency in response to the operation of the ball transmission 144 to indicate a change in the motion of the two machine tool slides, the reference pulses are recorded at a constant frequency, which as previously mentioned, will be assumed to be 60 cycles per second in the present embodiment. The reference pulses are recorded by the operation of the Aflip-flop circuit 79, shown diagrammatically in FIG. 8, which operates in the same manner as the flip-flop circuit 78, the flip-flop circuit 79 being connected to that section of the recording head 44 which cooperates with the reference channel of the magnetic tape. The flip-flop circuit 7 9, as previously mentioned, is actuated by the reference pulser mechanism 460.

It will be observed from the diagrammatic view in FIG. ll that the reference input to the X differential mechanism 295, the reference input to the Y differential mechanism 296, and the reference pulser mechanism 460, are all driven from the reference drive shaft 100 which is driven at a constant rate by the motor 22 through the gears 84, 98 and 99. Thus, the bevel gear 415 is keyed to the reference drive shaft 100 and it drives the two bevel gears 416 and 417 in unison. The bevel gear 417 transmits the reference input to the Y differential mechanism 296 through the gears 449, 450, 451 and 452. In like manner, the bevel gear 416 transmits the reference input to the X differential mechanism 295 through an identical gear train comprising the gears 423, 424, 426 and 427. In addition, the reference cam disc 461 of the reference pulser mechanism is mounted on the shaft 425 with the gear 424, as shown in FIG. 7 and diagrammatically in FIG. 1l, so that the cam disc 461 rotates in unison with the gear 424, the latter of course, being driven from the reference drive shaft 100 through the gears 416 and 423.

The disc 461 is provided with a cam 462 which is arranged to open a pair of normally closed switches 463 and 464 that are spaced 180 apart, as shown in FIG. 7. The switches 463 and 464 are identical to the switches 4'37 and 438, previously described, and operate to change the state of the reference electronic Hip-flop circuit 79 which is shown schematically in FIG. 8. When the switch 463 is actuated to an open condition it interrupts the circuit to the flip-flop 79 to effect a change in the state of the circuit to thereby effect a recording of a magnetic pole of positive polarity on the magnetic tape. When the switch 464 is actuated to an open condition it operates to change the state of the associated flip-flop circuit back to its original state and thereby effect a recording of a magnetic pole of negative polarity on the tape. The flip-flop circuits 4or square wave generators are contained within a protective casing 458 mounted on a platform 459 on which the entire tape recording apparatus is supported.

Therefore, three channels of intelligence will have been recorded on the tape; the X channel which will function to control motion of a machine slide member in an X direction; the Y channel which will function to control the motion of another machine slide member in a Y direction; and the reference channel to which the X and Y channels are related. On a playback of the magnetic tape in the control mechanism of a machine tool the reference channel recorded on the tape will serve to synchronize the control of the machine tool so that the motion of the slide members thereof will respond in exact accordance with the frequency of the electrical pulses obtained from the X and Y channels relative to the frequency of the pulses obtained from the reference ch-annel.

Thus, for the purpose of the present description it is assumed that as previously mentioned, the gear ratios are arranged so that the reference mechanical pulser is operated at a rate to cause the recording of reference pulses on the reference channel at a constant frequency of 60 cycles per second. At the same time the reference input is likewise transmitted from the reference drive i shaft 100 to the bevel gear 427 of the X differential mechanism 295. The gear ratios in the drive train to the differential mechanism 295 are arranged so that if the reference input to the bevel gear 427 is operating alone to drive the differential mechanism 295, the latter will rotate the cam disc 435 of the X mechanical pulser at a rate to produce a recording of the pulses on the magnetic tape at a frequency of cycles per second. Therefore, in the absence of any 'other influence, the `reference input to the differential mechanism 295, operating alone, would cause a recording of the pulses on the X channel of the type at a frequency of 60 cycles per second which corresponds with the frequency of the pulses recorded on the reference channel of the tape. Such correspondence in the two frequencies indicates that there is to benolmotion along Vthe X axis and the X machine tool slide is to remain at rest. A motion along the X or Y axes is indicated when the frequency of the pulses on the X or Y channels respectively deviate from the frequency of the pulses on the reference channel.

Such deviation in the frequency -of the pulses on the X channel is obtained by the operation of the ball transmission 144. The output of the ball transmission through the X take-off wheel 188 is transmitted through the gear train previously described to the bevel gear 386 of the differential mechanism 295 to constitute the X input to the differential mechanism. This X input is added algebraically to the `reference input transmitted to the bevel gear 427 to either increase or decrease the rate of rotation of the cam disc 435 of the mechanical pulser 430 depending upon the direction of rotation of the takeoff wheel 188. If the take-off wheel 188 is rotated in a direction to cause rotation of the bevel gear 386 in what may be termed a positive direction, its input will be added by the differential mechanism 295 to the reference input to increase the rate of rotation of the cam disc 435 so that the pulses will be recorded on the X channel of the magnetic tape at a frequency greater than 60 cycles per second. Since the frequency of the X pulses is greater than the reference frequency, the motion along the X axis will be in a positive direction, and the more the frequency on the X channel exceeds 60 cycles per second, the faster the rate of travel that is called for along the X axis in a positive direction.

On the other hand, if the take-off wheel 188 is rotated in the opposite direction it will cause rotation of the bevel gear 386 in the opposite, or what may be termed a negative direction. The X input to the `differential mechanism will then be subtracted rather than added t0 the reference input by the differential mechanism to decrease the rate of rotation of the cam disc 435 so that the pulses will be recorded on the X channel of the magnetic tape at a frequency that is less than 60` cycles per second. Since the frequency of the X pulses is less than the reference frequency the motion called for along the X axis will be in a negative direction, and the lower the frequency of the pulses on the X channel below 60 cycles per second, the faster the rate of travel that is called for along the X axis in a negative direction.

The apparatus operates in an identical manner to record the same data for controlling the motion along the Y axis. The reference input from the reference drive shaft 106 is transmitted from the gear 417 to the bevel gear 452 of the Y differential mechanism 296 to constitute the reference input to the Y differential mechanism. The movement along the Y axis is determined by the input to the Y differential mechanism from the Y take-off wheel 189 of the ball transmission 144, the rotation of the take-off wheel 189 being transmitted through the previously described gear train to the bevel gear 403 of the Y differential mechanism 296. This input is either subtracted or added to the reference input from the bevel gear 452 by the differential mechanism depending upon the direction of rotation of the take-off wheel 189 to regulate the rate of rotation of the cam disc 455 and thereby control the frequency of the pulses recorded on the Y channel of the magnetic tape. On playback of the record, the frequency of the pulses on the Y channel of the tape is compared with the frequency of the pulses on the reference channel of the tape to establish the motion along the Y axis in the same manner as described for the X axis. It is therefore apparent that the motion along both the X and Y axes may be established by simply steering the drive wheel 161 of the ball transmission 144 to adjust the distribution of the output amongst the two take-off wheels 188 and 189.

It is essential that the operator of the apparatus be apprised of the amount of movement recorded along both the X and Y axes during the operation of the machine. To this end, a pair of mechanical counters 467 and 468 are provided, as illustrated in FIGS. 2, 5, 7 and 1l. The 

1. THE METHOD OF RECORDING THE MOVEMENT OF THE MOVABLE MEMBERS OF A MACHINE FOR PERFORMING A SPECIFIC OPERATION COMPRISING; RESOLVING A MOTION REPRESENTATIVE OF A PATH IDENTIFIED WITH RESPECT TO X AND Y COORDINATES TO OBTAIN TWO SINE-COSINE RELATED MOTION COMPONENTS REPRESENTING THE MOVEMENTS OF THE MOVABLE MEMBERS OF THE MACHINE; APPLYING THE FIRST OF SAID MOTION COMPONENTS TO PRODUCE MOTION PULSES AT A FREQUENCY CORRESPONDING TO THE VALUE OF THE FIRST MOTION COMPONENT; APPLYING THE SECOND OF SAID MOTION COMPONENTS TO PRODUCE MOTION PULSES AT A FREQUENCY CORRESPONDING TO THE VALUE OF THE SECOND MOTION COMPONENT; PRODUCING REFERENCE PULSES AT A CONSTANT FREQUENCY; AND RECORDING THE MOTION PULSES AND THE REFERENCE PULSES ON A RECORDING MEDIUM TO FORM A RECORD; WHEREBY THE RECORD CAN BE PLAYED BACK AND THE FREQUENCIES OF THE MOTION PULSES MAY BE COMPARED WITH THE CONSTANT FREQUENCIES OF THE REFERENCE PULSES TO CONTROL THE RATE AND DIRECTION OF MOVEMENT OF THE MOVABLE MEMBERS. 